A noncompliant left ventricle is a common finding in patients with idiopathic hypertrophic subaortic stenosis (IHSS). Secondarily, arrhythmias produce symptomatic reduction of the cardiac output, which is seldom tolerated. Following left ventricular myotomy and myectomy with complete reduction of the LV-aortic gradient and significant improvement in the quality of life, these patients continue to tolerate poorly arrhythmic disturbances.